I'm working on physics homework and I wanted to know why the current in this circuit (and some other circuits I see in my homework) moves away from the negative terminal.


This is the problem that sparked the question. It asks me to find what the largest voltage possible is if the bar at the bottom of the circuit is to rest there without breaking the circuit. The problem only began to make sense to me when I realized that the current was moving counter-clockwise in the circuit.

But why does the current in this circuit move counter-clockwise? I've tried reading my textbook for answers, but I still don't know how to correctly determine which direction current flows in a circuit. I read that it moves toward decreasing potential, so I assumed it would move from the bigger bracket toward the smaller bracket at the battery with potential V, and then continue on from there in that direction, in the clockwise direction. However, in this example it goes COUNTER-clockwise. Why? Shouldn't it just move toward negative potential all the time?


Current flows from higher to lower potential in the external circuit not through the battery. So the current flows from the larger bracket as you call it, anticlockwise, then to the smaller bracket. A good way to remember this is to note that in the symbol for DC source, there is no internal line connecting the brackets, so if there is any current flow, it is from one bracket to another via the externally connected circuit.

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  • $\begingroup$ Ah! That makes so much sense! I see that I was fundamentally wrong in how I thought about the flow of current due to a battery. Thanks for the help gregsan! $\endgroup$ – Max Nov 11 '17 at 16:45

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